Generally, blood purification therapy, for example, dialysis therapy, uses a blood circuit containing a flexible tube to circulate the blood of the patient extracorporeally. This blood circuit mainly contains an arterial blood circuit with an arterial needle installed on the end that collects blood from the patient, and a venous blood circuit with a venous needle installed on the end that returns blood to the patient; and the blood circulating extracorporeally is purified by interposing a dialyzer between these arterial blood and venous blood circuits.
The dialyzer is constituted such that multiple hollow fibers are arranged inside; the blood passes through the interiors of these hollow fibers, and dialysate can flow on the outside (between the outer surfaces of the hollow fibers and the inner surface of the chassis). The hollow fibers have micro-holes (pores) in the wall surfaces to form a blood purification membrane, and blood waste materials and the like that pass through the interior of the hollow fibers pass through the blood purification membrane and are discharged into the dialysate while the blood which has been purified by eliminating the waste materials is returned to inside the body of the patient. A water removal pump to remove water from the blood of the patient is arranged inside the dialysis apparatus so that water is removed during dialysis therapy.
In this regard, for example, when the arterial needle and the venous needle are inserted in and around the shunt (a part in which an artery and a vein are surgically connected) and circulation extracorporeally is performed, blood recirculation may occur in which the blood that has been purified and returned into the body of the patient from the venous needle in question, is re-introduced from the arterial needle without passing through the organs and the like of the patient. If this kind of blood recirculation occurs, the purified blood is circulated extracorporeally once again and the volume of blood requiring purification that is circulating extracorporeally is reduced by that amount, leading to the problem that the blood purification efficiency is reduced.
Nonetheless, in the past a dialysis apparatus was proposed that, by rapidly driving the water removal pump for a short period of time only, imparted a specific peak to change the blood concentration circulating extracorporeally, and extracorporeal blood recirculation could be detected by using this peak as a marker (see, for example, Japanese Patent Application Publication No. 2000-502940). According to the dialysis apparatus disclosed in this patent document, a sensor to detect the blood concentration (sensor to detect the hemoglobin concentration) was arranged in the arterial blood circuit, and blood recirculation during dialysis therapy was detected by using this sensor to detect the specific peak.